YES O(n^2) TRS: { a__zeros() -> cons(0(), zeros()), a__zeros() -> zeros(), mark(cons(X1, X2)) -> cons(mark(X1), X2), mark(0()) -> 0(), mark(zeros()) -> a__zeros(), mark(tail(X)) -> a__tail(mark(X)), a__tail(X) -> tail(X), a__tail(cons(X, XS)) -> mark(XS) } DUP: We consider a non-duplicating system. Trs: { a__zeros() -> cons(0(), zeros()), a__zeros() -> zeros(), mark(cons(X1, X2)) -> cons(mark(X1), X2), mark(0()) -> 0(), mark(zeros()) -> a__zeros(), mark(tail(X)) -> a__tail(mark(X)), a__tail(X) -> tail(X), a__tail(cons(X, XS)) -> mark(XS) } Matrix Interpretation: Interpretation class: triangular [X1] [1 2][X1] [0] [tail]([X0]) = [0 1][X0] + [3] [X1] [1 2][X1] [1] [a__tail]([X0]) = [0 1][X0] + [3] [X1] [1 2][X1] [0] [mark]([X0]) = [0 1][X0] + [2] [1] [a__zeros] = [3] [0] [zeros] = [1] [0] [0] = [1] [X3] [X1] [1 0][X3] [1 0][X1] [0] [cons]([X2], [X0]) = [0 1][X2] + [0 1][X0] + [1] Qed